The rapid calculation and display of computer graphical images, e.g., three-dimensional objects in video games, often relies upon the rendering of images using tessellated surfaces, such as triangles or other tiled surfaces. Disparities between the shapes of a target surface and a tessellated surface rendering the target surface, can lead to visual artifacts, such as faceting. To reduce such artifacts, shading or vertex normal vectors can be calculated by interpolating normal vectors over the tessellated surface. Then the shading normal vectors are applied, as part of the rendering program, to make the rendered surface appear more smooth or continuous.